The present invention relates to a scroll compressor in which a spiral lap of a fixed scroll part and a spiral lap of a turning scroll part are meshed with each other to form a compression chamber, a rotation-restraining mechanism restrains the turning scroll part from rotating to turn the turning scroll part along a circular orbit, a compression chamber formed between the spiral lap of the fixed scroll part and the spiral lap of the turning scroll part moves while changing a volume of the compression chamber, thereby compressing sucked refrigerant and discharging the refrigerant.
In domestic or service freezing air conditioning field, reciprocating type compressors, rotary type compressors and scroll type compressors are used as freezing air conditioning hermetical type compressors. Such reciprocating type compressors, rotary type compressors and scroll type compressors are developed while making full use of their characteristics of costs and performance.
If compressors are aimed at enhancing the degree of soundproofing and maintenance free, a hermetical type compressor in which a compressing mechanism and a motor mechanism are accommodated is used. The mainstreams of the hermetical type compressor are the scroll type compressors and rotary type compressors.
An example of a conventional scroll compressor will be shown. FIG. 8 is a sectional view of the scroll compressor.
In the scroll compressor, a fixed scroll part 2 and a turning scroll part 4 form a compression chamber 5. In the fixed scroll part 2, a spiral lap 2a rises from a mirror plate 2b. In the turning scroll part 4, a spiral lap 4a rises from a mirror plate 4b. The compression chamber 5 is formed between the mirror plate 2b and the mirror plate 4b by meshing the spiral lap 2a and the spiral lap 4a with each other. A rotation-restraining mechanism restrains the turning scroll part 4 from rotating, and the turning scroll part 4 turns along a circular orbit. The compression chamber 5 moves while changing its volume by the turning motion of the turning scroll part 4. In the compression chamber 5, sucked refrigerant is compressed, and the compressed refrigerant is discharged out. A predetermined back pressure is applied to an outer peripheral portion of the turning scroll part 4 and a back surface of the spiral lap so that the turning scroll part 4 is not separated from the fixed scroll part 2 and is not overthrown.
Refrigerant gas sucked by the intake pipe 1 passes through an intake chamber 3 of the fixed scroll part 2 and is trapped in a compression chamber 5 formed by meshing the fixed scroll part 2 and the turning scroll part 4 with each other, and the refrigerant gas is compressed while reducing a volume of the compression chamber 5 toward a center of the fixed scroll part 2, and the refrigerant gas is discharged from a discharge port 6. A back pressure chamber 8 is formed by being surrounded by the fixed scroll part 2 and a bearing 7. It is necessary that the back pressure chamber 8 always has a back pressure of such a degree that the turning scroll part 4 is not separated from the fixed scroll part 2, but if the back pressure is excessively great, the turning scroll part 4 is strongly pushed against the fixed scroll part 2, a scroll sliding portion is abnormally worn and the input is increased. Thereupon, there is provided a back pressure adjusting mechanism 9 for always keeping the back pressure constant. The back pressure adjusting mechanism 9 comprises a passage 10 having a valve 11. The passage 10 passes through the fixed scroll part 2 from the back pressure chamber 8 and is in communication with the intake chamber 3. If a pressure in the back pressure chamber 8 becomes higher than a set pressure, the valve 11 is opened, oil in the back pressure chamber 8 is supplied to the intake chamber 3 so that a pressure in the back pressure chamber 8 is maintained at a constant intermediate pressure. The intermediate pressure is applied to the back surface of the turning scroll part 4 so that the turning scroll part 4 is not overthrown during the operation. The oil supplied the intake chamber 3 moves to the compression chamber 5 together with the turning motion of the turning scroll part 4 to prevent the refrigerant from leaking from between the compressed spaces.
When carbon dioxide is used as the refrigerant and the compressor is operated under a pressure equal to or higher than a critical pressure, a pressure different between discharging pressure and suction pressure of the compressor is higher, by about 7 to 10 times, than a pressure different of the conventional refrigeration cycle in which chlorofluorocarbons are used as the refrigerant. For this reason, there is a problem that in the compression chamber 5 formed between the fixed scroll part 2 and the turning scroll part 4, the leakage from tip clearance of the laps 2a and 4a is increased and the performance is deteriorated.
According to a scroll compressor described in Japanese Patent Application Laid-open No. 2001-207979 for example, in order to reduce the leakage from between a companion""s mirror plate and a tip clearance of the lap, a tip seal groove is formed in the tip clearance of the scroll lap, and a tip seal is mounted in the groove. However, this scroll compressor has problems that the sliding loss caused by contact of the tip seal is increased, the number of parts is increased, the number of processing steps is increased and thus, the productivity is deteriorated.
The present invention has been accomplished in view of the conventional problems, and it is an object of the invention to provide an efficient and reliable scroll compressor having a simple and inexpensive structure when carbon dioxide is used as refrigerant.
A first aspect of the present invention provides a scroll compressor in which a spiral lap of a fixed scroll part and a spiral lap of a turning scroll part are meshed with each other to form a compression chamber, a rotation-restraining mechanism restrains the turning scroll part from rotating to turn the turning scroll part along a circular orbit, a compression chamber formed between the spiral lap of the fixed scroll part and the spiral lap of the turning scroll part moves while changing a volume of the compression chamber, thereby compressing sucked refrigerant and discharging the refrigerant, wherein carbon dioxide is used as the refrigerant, an amount of lubricant to be supplied into the compression chamber is set to a ratio of 2% by weight or more and less than 20% by weight of an amount of the lubricant trapped in the compression chamber when a suction stroke of the refrigerant is completed.
According to this aspect, the lubricant supplied to the compression chamber functions as seal oil, and it is possible to reduce the leakage from tip clearance and sidewalls of the laps. Further, it is possible to minimize the increase of loss caused by sucking and heating. Since it is unnecessary to provide a tip seal, it is possible to reduce the costs without increasing the number of parts.
According to a second aspect of the invention, in the scroll compressor of the first aspect, a volume of the intake chamber of the fixed scroll part is 20% or more of a displacement volume of the compression chamber.
According to this aspect, since it is possible to sufficiently-mix the lubricant and the refrigerant before the refrigerant is compressed, it is possible to further enhance the sealing ability of the compression chamber and to reduce the leakage.
According to a third aspect of the invention, in the scroll compressor of the first aspect, the turning scroll part is provided therein with a throttle hole through which lubricant flows.
According to this aspect, it is possible to inexpensively realize the means for supplying lubricant to the compression chamber 5 in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the sucked refrigerant amount.
According to a fourth aspect of the invention, in the scroll compressor of the first aspect, the compressor further comprises a throttle hole through which lubricant flows intermittently by driving the turning scroll part.
According to this aspect, lubricant can be supplied to the compression chamber 5 in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the sucked refrigerant amount, and the supply amount can be adjusted with respect to the variation in refrigerant circulation amount. Therefore, it is possible to provide a more efficient scroll compressor.
According to a fifth aspect of the invention, in the scroll compressor of any one of the first to fourth aspects, oil having polyalkylene glycol as main ingredient is used as the lubricant.
According to this aspect, it is possible to enhance the machine efficiency with respect to the entire operation region and to reduce the leakage loss and thus, it is possible to provide a more efficient scroll compressor.
According to a sixth aspect of the invention, in the scroll compressor of any one of the first to fourth aspects, oil having polyol ester as main ingredient is used as the lubricant.
According to this aspect, under a condition in which the refrigerant circulation amount is large, the sealing ability of the compression chamber is further enhanced and it is possible to provide a more efficient scroll compressor.
A seventh aspect of the invention provides a scroll compressor in which a spiral lap of a fixed scroll part and a spiral lap of a turning scroll part are meshed with each other to form a compression chamber, a rotation-restraining mechanism restrains the turning scroll part from rotating to turn the turning scroll part along a circular orbit, a compression chamber formed between the spiral lap of the fixed scroll part and the spiral lap of the turning scroll part moves while changing a volume of the compression chamber, thereby compressing sucked refrigerant and discharging the refrigerant, wherein carbon dioxide is used as the refrigerant, oil having polyalkylene glycol as main ingredient is used as the lubricant, the turning scroll part is provided therein with a throttle hole through which the lubricant flows, lubricant is supplied to the compression chamber by the throttle hole in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the refrigerant trapped in the compression chamber when a suction stroke of the refrigerant is completed.
According to this aspect, the lubricant supplied to the compression chamber functions as seal oil, and it is possible to reduce the leakage from tip clearance of the laps and leakage from sidewalls. Further, it is possible to minimize the increase of loss caused by sucking and heating. Since it is unnecessary to provide a tip seal, it is possible to reduce the costs without increasing the number of parts, and it is possible to inexpensively realize the means for supplying lubricant to the compression chamber 5 in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the sucked refrigerant amount. Further, since oil having polyalkylene glycol as main ingredient is used, it is possible to enhance the machine efficiency with respect to the entire operation region and to reduce the leakage loss and thus, it is possible to provide a more efficient scroll compressor.
An eighth aspect of the invention provides a scroll compressor in which a spiral lap of a fixed scroll part and a spiral lap of a turning scroll part are meshed with each other to form a compression chamber, a rotation-restraining mechanism restrains the turning scroll part from rotating to turn the turning scroll part along a circular orbit, a compression chamber formed between the spiral lap of the fixed scroll part and the spiral lap of the turning scroll part moves while changing a volume of the compression chamber, thereby compressing sucked refrigerant and discharging the refrigerant, wherein carbon dioxide is used as the refrigerant, oil having polyol ester as main ingredient is used as the lubricant, the turning scroll part is provided therein with a throttle hole through which the lubricant flows, lubricant is supplied to the compression chamber by the throttle hole in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the refrigerant trapped in the compression chamber when a suction stroke of the refrigerant is completed.
According to this aspect, the lubricant supplied to the compression chamber functions as seal oil, and it is possible to reduce the leakage from tip clearance of the laps and leakage from sidewalls. Further, it is possible to minimize the increase of loss caused by sucking and heating. Since it is unnecessary to provide a tip seal, it is possible to reduce the costs without increasing the number of parts, and it is possible to inexpensively realize the means for supplying lubricant to the compression chamber 5 in the proportions of 2% by weight or more and less than 20% by weight of the lubricant to the sucked refrigerant amount. Further, since oil having polyol ester as main ingredient is used as the lubricant, under a condition in which the refrigerant circulation amount is large, the sealing ability of the compression chamber is further enhanced and it is possible to provide a more efficient scroll compressor.